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Old 03-24-2021, 06:54 PM   #16
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120/420 and 190/420 (16.5). These are Pirelli's.
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Old 03-24-2021, 07:48 PM   #17
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120/420 and 190/420 (16.5). These are Pirelli's.
Pirellis? What model are they? I was under the impression they'd DCed 16.5.
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Old 03-24-2021, 08:07 PM   #18
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These are new production, made at our request. Not sure if they'll do that again. They're Super Corsa slicks.
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Old 03-26-2021, 05:18 PM   #19
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So a quick (brusque might be a better word) conversation with Race Tech tells us that they no longer offer any sort of chassis setup work, at all. And they can't be bothered to try to find any records they may have on the bike's original setup, which they did when the bike was built a dozen years ago. Simply not interested in being helpful in any way.

So we are on our own for figuring out what it is that we've got.

First step- new tires. Ordered.
Second step- take it in to Lee's for a spring swap.
Third step-???
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Old 03-29-2021, 10:11 AM   #20
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You're trying to sort out the fork too? What year Marzocchi is it? Question: how much are you willing to throw at it? We know people who have been at racetech forever, but they probably won't remember what they put on it. If you want to sort the suspension, take off the fork/ shock and send it out to a shop who does custom work. They'll be able to figure some things out for you...but nothing's for free.

There's lots of people that can help, but I'd still start with Gerry at GP frame and wheel and get some chassis numbers correct first, then rear spring. Forks are the last thing I'd do...
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Old 03-29-2021, 11:17 AM   #21
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I think the fork isn’t a problem at the moment. At least, not an overriding problem, but it will need to be sorted out at some point.
It’s the original supermoto spec Marzocchi, which RaceTech shortened the travel on- and who knows what else they did. But a spring swap should be easy enough.
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Old 03-29-2021, 11:21 AM   #22
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Tally, since you are in San Diego, Id call Quintin at NextLevelCycles and ask him if he has an experience with these bikes or if he knows anyone that does. If that doesn't produce a lead, broaden your search and keep calling people until it does. Phone calls are free and you will save a lot of money and time if you can find someone that already knows a reasonable baseline setup for these bikes.

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You're trying to sort out the fork too? What year Marzocchi is it? Question: how much are you willing to throw at it? We know people who have been at racetech forever, but they probably won't remember what they put on it. If you want to sort the suspension, take off the fork/ shock and send it out to a shop who does custom work. They'll be able to figure some things out for you...but nothing's for free.

There's lots of people that can help, but I'd still start with Gerry at GP frame and wheel and get some chassis numbers correct first, then rear spring. Forks are the last thing I'd do...
Do you think Gerry actually has "correct" chassis numbers for such a frankenbike?

As TWF already said, sportbike numbers won't work.
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Old 03-29-2021, 01:37 PM   #23
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I don't think he'll have the numbers in a book, no, but he's built his fair share of frakenbikes (used to be co-owner of Motomorphic). His unique focus is on chassis measurements/ straightening so he should know a baseline for geometry numbers to get Tally into a usable range.

As you know, you've gotta get geometry correct first then move to springs rates, etc. Speaking of...I need to update our other thread on BW T2.
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Old 03-29-2021, 06:06 PM   #24
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Tally, since you are in San Diego, Id call Quintin at NextLevelCycles and ask him if he has an experience with these bikes or if he knows anyone that does. If that doesn't produce a lead, broaden your search and keep calling people until it does. Phone calls are free and you will save a lot of money and time if you can find someone that already knows a reasonable baseline setup for these bikes.



Do you think Gerry actually has "correct" chassis numbers for such a frankenbike?

As TWF already said, sportbike numbers won't work.

Jeremy T has already expressed a serious lack of interest in even looking at it, but I'm hoping we can twist his arm. I hadn't really thought of Quinten, even though I just saw him last month for the first time in a long while.
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Old 04-05-2021, 09:30 AM   #25
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Ok- we dropped the bike off at Lee’s this morning. Hopefully Jody and Jeremy can figure out the rear shock issue.
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Old 05-23-2021, 08:33 AM   #26
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All right- time for an update.

Jody at Lee’s changed the rear spring and revalved the shock, so now it has reasonable amounts of sag. He didn’t lengthen it to get more swingarm angle or anything like that- after some debate that was left alone.
He resprung and tuned the fork as well, since the Marzocchi Shiver has no ability to preload in any way.
New Metzeler SuMo slicks (thanks to Berto for the hookup) replaced the aged-out Bridgestones.

So now the instability has been greatly reduced. The bike is rideable now without the disconcerting feeling that it would spontaneously crash at any moment. It still has a hint of the wobble, but you have to do something to instigate it and it doesn’t self-augment.

I think a steering damper would take care of it just fine.

Now, it’s worth comparing to my Yammie F450 with an R6 front end. My bike is far from what anybody would call stable, but it isn’t wobbly, either. It’s quick-handling and easy to upset with ill-considered body movement, but it never feels as if it wants to shake you off.

The Husky F450’s problems, at this point, I think stem from trying to use the original fork in a shortened form. Because it’s a dirt bike fork and designed for a fair bit of rake, the trail at a steeper angle is just too short with the axle ahead of the legs.
Swapping to a set of sport bike forks could cure the problem, and that might be the final answer but it would be a shame to do that and throw away the custom triple made for the bike.

Last edited by Tally Whacker; 05-24-2021 at 11:15 AM.. Reason: Autocorrect miscorrections corrected.
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Old 05-24-2021, 10:16 AM   #27
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That definitely still sounds like a bike that would be terrible to push hard around a track. Stable bikes are fast bikes.

That was a lot of changes all at one time - diff shock spring, diff shock valving, diff fork springs, diff tires. Do you have any idea which one you'd do more to further improve the issue? Moving on to a 5th huge change may not be the best solution.
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Old 05-24-2021, 11:14 AM   #28
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That definitely still sounds like a bike that would be terrible to push hard around a track. Stable bikes are fast bikes.

That was a lot of changes all at one time - diff shock spring, diff shock valving, diff fork springs, diff tires. Do you have any idea which one you'd do more to further improve the issue? Moving on to a 5th huge change may not be the best solution.

Well, here's an interesting detail. When we go tthe bike back to my friend's house, we fired it up and I took it for a spin around the nighborhood and it felt dramatically improved from what it had been, but still not stellar. The wobbles never felt as if they were going to get out of control, in the sense that they died down after the initail input to start them. Before, they'd continue to propagate. They never developed into tank-slapper territory before, but definitely weren't confidence inspiring.
So after the shock, fork and tire work, it was better, but still a bit of an issue.

We checked the tire pressure, and it was way high- typical, right? Pump them up too much, then drop them to what you want trackside.
Anyhow, we dropped them to 26/23, as recommended, and I took the bike out again.
It was much better- almost as much of an improvement again as I'd experienced a few minutes before.
So that tells me that at least half of the initial problem was the tires. Not the fresh tires are set to proper pressure, life is much better. As it sits now, I'd take it out for a session on a track day and not be convinced I was going to wipe out.

So, 80-90% of the way there. At this point, without actually going to non-offset forks, a damper will do enough to make the bike acceptable.
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Old 05-25-2021, 03:28 PM   #29
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Can you get some scales and measure the weight on each tire? I have suspicions there's not enough weight on the front.
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Old 05-26-2021, 09:17 AM   #30
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A super digressive rear end will be terrible at keeping weight on the front. However, riding the bike on the street wouldn't really test that because you aren't WOT out of corners.

Using a damper to "fix" front end instabilities may lead to a bunch of crashes. If the instabilities are caused by improper loading of the front tire, you won't have grip. A damper isn't going to fix that.

My race bike rides like a tank on the street as the front end is so long when I'm not braking. Id be super worried if it was unstable at such slow speeds.
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